Gyakusatsu Happy End

High school student Kusakabe Makoto has to work all day to raise money for the treatment of his younger sister, who suffers from a serious illness. The father is unemployed, the mother ran away, leaving the children, bullying at work... Despite all this, he does not lose hope and continues to live for his sister. But having learned that she did not have long, Makoto falls into despair. Fear of the unknown causes him to take a different look at the value of human life.

(Source: Hakusensha, translated)